For example, in the printing business circles, binary data (also called monochrome data) of a printed matter is prepared as printing data, the binary data is outputted by a plotter device, which is a machine for exposing a film, and after development, it is transferred to a printing plate, and printing is performed. Normally, a system in the printing business circles is often constructed to expand data in a resolution peculiar to a plotter. This is because data for a fixed resolution, such as bitmap fonts constructed in units of dots and/or a conversion table for performing conversion to dot data, must be prepared on a system. Thus, in the case where more high resolution output system is installed, in addition to the present conversion table for performing conversion to dot data, bitmap fonts, and an expansion routine for the present resolution, it is necessary to add more conversion table for performing conversion to dot data, bitmap fonts, and an expansion routine for a high resolution, and there is a problem that a system change becomes enormous.
Accordingly, it is conceivable to adopt a method in which binary data of the present resolution is converted to binary data of a high resolution to perform printing. However, when a method is adopted in which the binary data of the present resolution is simply expanded and is complemented by copying, although black and white lines are uniformly arranged in the binary data of the present resolution as shown in FIG. 17A, if the data is converted to that of the high resolution, as shown in FIG. 17B, black and white lines are not uniformly arranged, and interference fringes occurs. Accordingly, the quality can not be obtained to such a degree that the data can be outputted to a film by a plotter.
For example, Japanese Patent No. 2848568 discloses an image processing apparatus in which binary data is converted to multi-value data, and after a desired image processing is carried out, a binary coding processing is carried out to again convert the multi-value data to the binary data. Although this publication states that a high quality image can be obtained at high speed and inexpensively, a problem in printing and the like is not considered.
That is, the problem that a dot gain (bleeding) occurs at the time of printing is not considered. There is a case where the degree of the dot gain becomes different according to types of output devices such as plotters. FIGS. 18A to 18D show examples. FIG. 18A shows digital data of 600 dpi, and FIG. 18B shows digital data of 1200 dpi. It is assumed that the area in the digital data of FIG. 18A is equal to that of FIG. 18B. However, when the data of FIG. 18A is printed, ink is applied in a range surrounded by a thick line as shown in FIG. 18C. On the other hand, when the data of FIG. 18B is printed, ink is applied in a range surrounded by a thick line as shown in FIG. 18D. When FIG. 18C is compared with FIG. 18D, the bleeding of FIG. 18D is low and the output density (area on which ink is applied) is small, whereas the bleeding of FIG. 18C is high and the output density is large. The bleeding of an output device having a low resolution is not necessarily high, and it varies according to the type of the output device. Besides, even if the resolution is the same, there is also a case where a difference occurs in the dot gain according to the output device.
As stated above, even if the area of the digital data is the same, the dot gain varies according to the output device, and as a result, the output density varies. Since the output result varies according to the output device, there is a problem that a user can not easily obtain an intended output result.